In the present study we propose a context wherein the endorsement rate of the scalar inference from ‘some’ to ‘not all’ either increases or decreases. It is known that people tend to interpret the quantifier ‘some’ as ‘not all’, though logically some means ‘some and possibly all’. However, we argue that this tendency to derive the scalar inference is variable and depends on the attitude of the reader or listener. When the ‘not all’ interpretation implies a confirmation of one’s attitude, we expect a higher endorsement rate of the inference. On the other hand when the ‘some and possibly all’ interpretation contains pro-attitudinal information, we expect a decrease in endorsement rate. These predictions are derived from Kunda’s theory of motivated reasoning (1990) and are supported by the data. Theoretical implications and suggestions for further research along this line are discussed.